Quote:
Originally Posted by Big Dave
Most travel trailers only travel about 500 miles a year. Unless you are one of those exceptions that travels more. the aero advantage is not worth the sacrifice of cost and interior space.
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Beat me to it
Not sure what the average is but the 1 percentile that puts many many more miles on isn't convincing enough to spend the money on R&D, implementation, etc.
All of that aside. I've been collecting a set of "Aero Rules" - here's a few that apply... I haven't really edited these - so pardon any goofy language
Names in the curly brackets are the source/author
Front Corners shall not have a radius to vehicle width ratio (r/W) no less than .045 {PAWLOWSKI}
Winshield angle from vertical shall be biased towards 90 degrees to reduce cD {G.W. CARR} but, the reduction is not as much as assumed. After beyond 60 degrees, there is almost no further reduction and may result in optical refraction and cabin heat issues {R. BUCHHEM, et. al.}
Lower Stagnation Point is better {R. BUCHHEM, et. al.}
Optimal roof camber ratio (a_r/l_r): .065 Where a_r is height above "flat" roofline and l_r is the length of "flat" roofline. Assumes FA remains constant. delta cD = -0.02 {R. BUCHHEM, et. al.}
Optimal taper angle is highly dependent on the "history" of flow. {HUCHO}
With increasing length, positive effect of tapering become weaker. "Bob-tailing" or truncating thet taper results in little loss in drag reduction {D.J. MAULL, W. KAMM}
Rear diffusers: For a given area ratio (outlet area/inlet area), long diffusers are better. The same drag reduction can be had with a smaller angle rather than a shorter diffuser). Small angle = 2 degrees {J. POTTHOFF}
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What does all that mean?
1. You don't need much corner rounding to make a significant impact
2. Both top and side profiles should bell outward in the center (camber)
3. For long objects - resisting resistance is futile...
I think it'd be cool to see these things made like large fiberglass boats. Prefab the "hull" - drop in the prefabbed innards... Glue on a "deck." That as opposed to the prefab wall on chassis method. If precise enough (and composite tooling can), a non square cabinet can be made a "standard" (routed wood or blanked/compressed composite) and allow for fast assembly that fits well.
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Now what should they do - aero aside?
Optimize material selection, manufacturing process and feature selection. Put cost, quality and innovative features as top priorities. Other factors should be secondary or tertiary considerations only if one of the three will benefit.